DEAR DR. DONOHUE: Our 44-year-old son was recently diagnosed with hepatitis C. He is taking no medications. He claims he feels fine, and he works 40 to 50 hours a week. Are there any precautions we should take when he visits in our home? – P.H.

ANSWER: Let me list the ways in which hepatitis C is spread. Unsterilized needles used in injections of illicit drugs are one of the main transmission routes for this virus. Blood transfusion used to be a source of spread, but it has not been since 1989, when a blood test to detect the virus was developed. Now the blood supply is safe, but transfusions before that time accounted for many infections. Sexual transmission is not common. Five different and well-designed studies have demonstrated a low risk of transmission between an infected spouse and noninfected partner. It happens only rarely–in less than 1.5 percent of such couples. Promiscuous sex, however, is dangerous and can account for some infections.

That still leaves a sizeable number of people who cannot pinpoint where they caught the virus.

The spread of virus within a family – to brothers, sisters, children, parents, aunts, uncles – is an extremely rare occurrence if it happens at all. You do not need to take any precautions when your son visits.

His plate and eating utensils need no special treatment. If he spends the night, his bedding will not pass the virus. You can hug your son, and he can play football with his brothers and sisters (if he has any and if they want to play). The only things that bear some watching are razors and toothbrushes that might have blood on them. Your son should not share those things with anyone.

Hepatitis is a widespread infection.

DEAR DR. DONOHUE: My friend’s son just had a bone marrow transplant. Could you please explain the procedure? When and for what is it done? – A.B.

ANSWER: The bone marrow is the central, spongy part of bone. It is the place where all blood cells – red, white and platelets – are produced.

For the treatment of some cancers, doctors have to give high doses of drugs, and that can wipe out a person’s marrow. That is one reason why marrow transplants are given. In other people, the marrow simply dries up and stops producing blood cells – another reason for a marrow transplant.

Marrow is obtained from a healthy donor with a special needle and syringe. The bone most often chosen is the large pelvic bone in the lowermost part of the back.

The marrow is filtered to remove any bony fragments and any fat. It is then infused into the patient in the same manner in which intravenous fluids are given.

It can take two to four weeks for the donor marrow cells to find their way to the recipient’s bone marrow and to take hold there. During this period of time, the recipient must be taken care of, with meticulous attention given to prevention of any infection. The recipient is vulnerable to infection during that time.

I gave you only a sample of the conditions where marrow transplants are used. There are many other occasions that call for this treatment.

DEAR DR. DONOHUE: My son is 8 and has taken allergy shots since he was 5. One lab test he had revealed a high eosinophil count. What are they, and what does a high count mean? – N.E.

ANSWER: Eosinophils are one of the five kinds of white blood cells. The function of white cells is infection-fighting. Normally there are only a few eosinophils, and their function includes attacking larger parasites, like intestinal worms. When a parasite infects the body, the eosinophil count goes up. It also rises with allergies; the reason why is obscure.

Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475.